jupyterlab/packages/mainmenu/test/util.ts

// Copyright (c) Jupyter Development Team.

import 'jest';
// Distributed under the terms of the Modified BSD License.

import { IMenuExtender } from '@jupyterlab/mainmenu';

import { Widget } from '@lumino/widgets';

/**
 * Given a widget and a set containing IMenuExtenders,
 * check the tracker and return the extender, if any,
 * that holds the widget.
 */
function findExtender<E extends IMenuExtender<Widget>>(
  widget: Widget,
  s: Set<E>
): E | undefined {
  let extender: E | undefined;
  s.forEach(value => {
    if (value.tracker.has(widget)) {
      extender = value;
    }
  });
  return extender;
}

/**
 * A utility function that delegates command execution
 * to an IMenuExtender.
 */
export function delegateExecute<E extends IMenuExtender<Widget>>(
  widget: Widget,
  s: Set<E>,
  executor: keyof E
): Promise<any> {
  const extender = findExtender(widget, s);
  if (!extender) {
    return Promise.resolve(void 0);
  }
  // Coerce the result to be a function. When Typedoc is updated to use
  // Typescript 2.8, we can possibly use conditional types to get Typescript
  // to recognize this is a function.
  const f = (extender[executor] as any) as (w: Widget) => Promise<any>;
  return f(widget);
}

/**
 * A utility function that delegates whether a command is toggled
 * for an IMenuExtender.
 */
export function delegateToggled<E extends IMenuExtender<Widget>>(
  widget: Widget,
  s: Set<E>,
  toggled: keyof E
): boolean {
  const extender = findExtender(widget, s);
  if (extender && extender[toggled]) {
    // Coerce the result to be a function. When Typedoc is updated to use
    // Typescript 2.8, we can possibly use conditional types to get Typescript
    // to recognize this is a function.
    const f = (extender[toggled] as any) as (w: Widget) => boolean;
    return f(widget);
  }
  return false;
}